The invention relates generally to a method for operating a melt-down gasifier or other apparatus for making liquid pig iron or steel starting material, which apparatus includes water cooled nozzles for introducing a measured quantity of oxygen-containing gas into the apparatus at as normal operating pressure. The invention relates specifically to the operation of such an apparatus in the event of a reduction of the supply of water for cooling the nozzles.
From DE-PS 30 34 539, a method for the direct production of molten pig iron from lumpy iron ore is known, in the course of which the iron ore is reduced to iron sponge in a reduction blast furnace by means of hot reduction gas, and is subsequently fed to a melt-down gasifier. In this gasifier, the heat and the reduction gas required are produced from charged coal and blown-in oxygen-containing gas. A fluidized bed is formed of the coal charged from above and the oxygen-containing gas blown into the lower part of the gasifier. The iron sponge particles likewise fed from above are slowed down and smelted in the fluidized bed. Radial oxygen nozzles which are fed from a ring conduit are provided at equal height and distributed over the perimeter of the meltdown gasifier for blowing-in the oxygen-containing gas. The nozzles are necessarily water-cooled in order to withstand the high temperatures prevailing in the interior of the melt-down gasifier and in particular in front of said nozzles. In this area in front of the nozzles, the fluidized bed is converted into a pasty or liquid matter due to the high temperatures prevailing there.
If a sudden failure of the feed of the said oxygen-containing gas occurs, said pasty or liquid mass is pressed outward into said water-cooled nozzles and solidifies therein. If subsequently the melt-down gasifier is again put into operation, the oxygen-containing gas cannot, or only in reduced quantity, be blown-in on account of the clogged nozzles.
Analogous problems arise from a scheduled stop of operation of the said melt-down gasifier with a slow reduction of operating pressure and reduction of the quantity of oxygen-containing gas. As the quantity of oxygen-containing gas is reduced, of, the flow the gas is no longer guaranteed through all nozzles. The pasty or liquid mass in the interior of the melt-down gasifier then penetrates into at least part of said oxygen nozzles and solidifies therein due to the water cooling. When the melt-down gasifier is again taken into operation, the oxygen-containing gas car flows in small quantities out of control through the channels between the cold nozzle extensions and the brick lining of the gasifier due to the clogging of the nozzles. Flame-ups and uncontrolled combustion occur at the hot spots, the flame directing itself also against the brick-work and even against the plate lining of the gasifier so that damage to same is unavoidable.
A failure of the cooling-water supply system for the nozzles results necessarily in damage to the nozzles. A failure of the cooling-water can cause the failure of the whole installation, so that there is the danger of liquid or pasty fluidized bed matter penetrating into the said nozzles and clogging the same.
An object of the present invention is therefore to prevent the clogging of the oxygen nozzles due to penetrating and subsequent solidification of fluidized bed matter in the case of the above mentioned failures or also scheduled changes during the operation of a melt-down gasifier, and also to prevent a thermal load on the nozzles in case of failure of the cooling-water supply to said nozzles which would cause damage thereof.